Hi everybody - long time! Well, there is actual biology behind these responses to enemas. Given properly and comfortably (which mostly excludes all enemas in medical settings) they relax the body incredibly and reduce blood pressure immediately. Nurse training even includes cautions to watch that the pressure does not fall dangerously low during an enema! The primary reason for these reactions is "vagus response" - stimulating not just the bowels but the vagus nerve, a primary parasympathetc nerve which runs throughout the body. Vagus response is also the reason behind the observation that digital - finger - stimulation through the rectum could cure intractable hiccups. I remember that when that got published gay guys would line up at clinics complaining of terrible hiccup problems which suddenly appeared!
This is not more widely appreciated because enemas are usually cloaked in embarrassment and unnecessary discomfort.
I have since researched and confirmed this, but I learned about this recently in a manuscript which a friend of a friend asked me to proofread. The book is about the growing up of the protagonist, which basically starts with an enema from a friend, breaking her self-imposed boundaries, or as she puts it, imposed by a narrative which she had not really examined. The story is not really sexual, though orgasms are on practically every page, and it is difficult but not humorless to read: the author herself says that reading it takes a dictionary and encyclopedia together, and possibly memorization of the whole corpus of English poetry. (She actually works in three words from Beowulf!). It also relates her trying to get her boyfriend to let her put in his suppositories. The book is actually intended as a very serious work, over 450 pages, in the general form of a journal. I find the protagonist/author personally very attractive. I mention all of this because if anyone is interested the author plans to post it somewhere unless and until anyone wants to publish it. I will share the link when and if she does post it, though I caution that it is more a book of "embodied, wet philosophy" than a bottoms one.
To get personal for a moment, I also find comfortable enemas accompanied by massage very deeply relaxing and banishing stress quickly. And by the way, both guys and gals have vagus nerves!
-- Jillie Ann